Light-emitting diodes (LEDs) have been widely used in the applications of lighting and backlighting. Different applications of the LEDs require different color lighting and different powers of the LEDs. For all types of LED that are currently available, the best performance is often exhibited in a constant-current driving. Thus, a power supply circuit that is designed for driving LED based circuit must be of the characteristics of supplying a constant current output. Often, a constant current regulator is used to provide the desired constant-current power supply. In all types of circuit, to ensure constant and identical current flowing through all the LEDs, the LEDs have to be connected in series.
Various types of constant current regulators are available, including buck type constant current regulator and boost type constant current regulator.